1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer-readable medium storing a program for performing the image processing method, and more particularly to color matching processing of input digital image data.
2. Description of the Related Art
A technique for matching color properties of an input device and color properties of an output device has been used recently, when color data generated on a computer is output by a color printer or a color multifunction peripheral (hereinafter referred to as a “color MFP”).
A widely used example of this technique includes color matching processing using an International Color Consortium (ICC) profile.
This method is achieved by interpolation processing using look-up table (LUT) information written in the ICC profile. Accordingly, the process can be performed at high speed, but depending on a color interpolation precision, a difference in color properties between input and output devices may result in different colors as a result of color matching processing.
To meet this issue, a technique for improving the color interpolation precision, i.e., a high-precision color correction technique using Windows® Color System (WCS) has been suggested and carried out.
The WCS generates and uses a color profile in eXtensible Markup Language (XML) for each of modules of a device, a viewing condition, and color gamut mapping. The color profile generated for each module is used by Color Infrastructure & Translation Engine (CITE).
FIG. 15 illustrates an overview of CITE processing 1501 in the WCS. In FIG. 15, a Color Device Model Profile (CDMP) 1502 describes measured values of input and output devices. A measured value of the input device is data representing a correspondence (input color property) between a color value at which the input device images a color patch or a color value at which the input device displays the color patch (L*a*b value) and a colorimetric value of the color patch (L*a*b* value output by a measuring instrument). Further, a measured value of the output device is data representing a correspondence (output color property) between a color value at which the output device prints a color patch and a colorimetric value of the color patch. A Color Appearance Model Profile (CAMP) 1503 is defined based on a visual system of human being. In general, a color appearance model such as CIECAM02 recommended by International Commission on Illumination (CIE) is used. The color appearance model is a model for predicting how a color appears according to viewing conditions having different characteristics in view of chromatic adaptation. The CIECAM02 uses equal-energy white (X=Y=X=100) to perform correction in view of incomplete chromatic adaptation in color prediction processing. Theoretically, equal-energy white is considered to be perceived as being white by human being. When a display image on a monitor and an output image from a printer (printed product) arranged side by side are viewed, the visual system tries to adapt to both of white on the monitor and white in viewed light, i.e., ambient light reflected by the printed product. Accordingly, the color matching precision can be improved by using an adapted white point in view of partial adaptation. The color appearance model is described in N. Moroney, M. D. Fairchild, C. Li, M. R. Luo, R. W. G. Huntand, T. Newman, “The CIECAM02 Color Appearance Model”, Proc. IS&T/SID10th IS&T/SID Color Imaging Conference (2002). A color gamut map model profile (GMMP) 1504 corresponding to rendering intent of ICC serves as a mapping model for color conversion. The GMMP is implemented with mapping algorithms for respective intents, which are divided into common processing, i.e., baseline, and plug-ins uniquely set by a vendor. For example, if this intent is colorimetric, luminosity clipping processing is determined to be executed.
A device models processing unit 1505 corresponds to mutual conversion processing between device-dependent color of ICC profile and device-independent color, i.e., Profile Connection Space (PCS), and carries out processing upon reading the CDMP 1502. A CAM processing unit 1506 reads the CAMP 1503, and performs mutual conversion processing from a device-independent space to a viewing condition independent space. A Gamut Map Models processing unit 1507 reads the GMMP 1504, and performs color conversion.
As described above, the CITE processing 1501 can use the above CDMP, CAMP, and GMMP to perform color conversion.
The CITE processing 1501 can achieve a high-precision color correction by performing this WCS processing. However, since the CDMP, CAMP, and GMMP are interpreted to dynamically perform color conversion, the processing load is large, and it is difficult to perform the processing at high speed.
Japanese Patent Application Laid-Open No. 2005-136752 discusses that a plurality of color conversion tables corresponding to an ink configuration are prepared in advance, and when the color space of an output side is standard, the previously-prepared color conversion table is used to reduce the above processing load to perform color conversion at high speed.
In the technique discussed in Japanese Patent Application Laid-Open No. 2005-136752, whether the output color space is standard is determined based on the ink configuration, and thereupon, control is performed to choose whether the previously-prepared color conversion is used or a color conversion table is generated according to the ink configuration from the existing ink conversion tables.
However, Japanese Patent Application Laid-Open No. 2005-136752 does not discuss that a color conversion table is generated from each profile when the settings of a viewing condition, an input color space, and color gamut mapping are not standard. Therefore, the technique discussed in Japanese Patent Application Laid-Open No. 2005-136752 cannot achieve both of the data processing improvement and the high-precision color correction.